Combination switch and variable resistor



March 3, 1964 s. o. BENDER 3,123,795

COMBINATION SWITCH AND VARIABLE RESISTOR Filed Nov. 29, 1961 3 Sheets-Sheet 1 p i /0 32 Immmm IIHHHHI 7 3f 5 @w p@ ""Hllmmw 32 FIG. 2

""HIHHHHHI INVENTOR STANLEY o. BENDER ATTQRNEY COMBINATION SWITCH AND VARIABLE RESISTOR Filed Nov. 29, 1961 March 3, 1964 s. o. BENDER 3 Sheets-Sheet 2 ll r!" "17 l II: I. 5''

FIG. 4.

INVENTOR STANLEY O. BENDER BY ,6 M

ATTORNEY March 3, 1964 s. o. BENDER COMBINATION SWITCH AND VARIABLE RESISTOR 3 Sheets-Sheet 35 Filed Nov. 29, 1961 FIG. 8.

INVE NTOR STANLEY O. BENDER ATTORNEY United States Patent 3,123,795 CfilvilllNATiflN SWHTCH AND VARlAhLE Stanley 0. Bender, Asheville, Nil, assignor to CTF: Corporation, Elldiart, End, a corporation of Indiana Filed Nov. 29, 2 .961, Ser. No. 155,555 7 Claims. (Qt. 333-172) This invention relates generally to a combination varia ble resistor and switch, and, in particular, to a combination variable resistor and switch specifically designed to effect an economy in parts so that the control will ocoupy a minimum amount of space.

In the hearing aid field, where the entire unit is to be mounted in the temple of the eyeglasses of the wearer, it is extremely important that the controls for the hearing aid be as physically small as possible. It is also advantageous to combine the two controls that need to be operated by the wearer: the on-oif switch and the volume control. By combining these controls, only one control knob is needed which greatly simplifies the construction of the housing for the unit. Also in the case of the temple mounted unit, it is important to have only one control knob, since the operator will usually want to make adjustments while wearing his glasses, and consequently, will not be able to watch what he is doing. With only one control knob to adjust, there will be no possibility of his turning the wrong knob.

Further, by combining the switch and volume control and arranging the switch to be operated at the point where the volume is the lowest, the possibility of turning on the unit with the volume control set high with the irritating blast of sound that follows, is eliminated.

Therefore, it is the principal object of this invention to provide an extremely small combination variable resistor and switch. It is an additional object of this invention to provide a combination variable resistor and switch which employs a minimum number of parts and whic employs parts which are common to both the variable resistor and switch but which perform different functions for each.

It is also an object of this invention to provide a switch which is so arranged and constructed that the movable contact moves into and out of engagement with the stationary contact with a wiping action.

The invention consists of a combination variable resister and switch. The variable resistor has a base, a knob rotor or contact carrier and a shaft with the usual terminals, contacts, and a resistive path supported by the base. The shaft is fixed to the base and rotatably supports the knob rotor, and also holds the rotor in position against the base. It also functions as the stationary contact of the switch while on the other side it acts as one terminal of the switch. By forming the rotor and the base with appropriate cavities which complement each other, the inner workings of the variable resistor can be housed by these members. The switch consists of a stationary contact and a movable contact, and means for moving the two contacts into and out of engagement. The stationary contact is provided by the end of the shaft which extends out from the rotor side of the control. The movable contact is a U-shaped member of resilient material which is arranged with one arm attached to the base and one arm in position against the end of the shaft on the opposite side from the base. The means for moving the movable contact to open and close the switch is located on the rotor and consists of a cam which engages the movable contact and forces it out of engagement with the shaft during a portion of the rotation of the rotor. In addition, a boss is provided on the end of the shaft acting as the stationary contact which makes point contact with Patented Mar. 3, 1964 the movable contact in such a way that the operating means causes a lateral and longitudinal movement as well as a vertical movement between the contacts when the switch is opened and closed. This lateral and longitudinal movement results in a wiping action between the contacts when the switch is opened and closed which is very desirable.

Another important feature of the invention is the unique design which combines the variable resistor and switch in such a way as to realize a real economy of parts, thus allowing a substantial reduction in the overall size of the control.

The invention will now be described in detail in connection width the attached drawings in which:

FIGURE 1 is a side view of the control looking at the base side;

FIGURE 2 is a side view of the control showing the rotor side-the opposite side from FIGURE 1;

FIGURE 3 is a top view of the control showing the terminals of the variable resistor;

FIGURE 4 is a cross-section through the control taken along line 4-4 in FIGURE 3;

FIGURES 5 and 6 show the cam action which opens and closes the switch;

FIGURE 7 is an enlarged view of the switch contact illustrating the wiping action which occurs when the switch is opened and closed; and

FIGURE 8 is a top view of a portion of the stationary contact illustrating the path followed by the point of contact between the two contacts as the switch is opened and closed.

In describing the control in detail, we will first discuss the arrangement of the members as they perform the function of a variable resistor and then we will discuss the components which make up the switch section of the control.

T he three large components of the variable resistor are the base lit, the rotor or knob Ill and the shaft 112. r'lhe shaft has an enlarged head 13 and three sections of varying diameter indicated at lid, 15, and do.

The base *ltl is provided with an opening through its center approximately the same size as the section 15 of the shaft so that by placing the base on this section of the shaft, against the shoulder formed between the two sections and i5 and staking the shaft as shown at I7, the base is permanently assembled on the shaft.

The snob I l is also equipped with a hole through its center. This hole is slightly larger than section 14 of the shaft so that when assembled in the manner shown in FIGURE 4, the rotor lll will be free to rotate on the shaft, with respect to both the shaft and the base It The rotor is, of course, held on the shaft by the enlarged head 13 and the base it).

The rotor is also equipped with an annular ring 18 which provides an annular cavity to house the current carrying members of the variable resistor. The flange or ring 18 also has a portion 19 of increased thickness which is arranged to engage the lug ill} on the base to limit the amount of rotation of the rotor in each direction.

The current carrying members of the variable resistor are the resistive element 21, which is mounted on the base and which is arcuate in the conventional manner; the contactor 22, which is attached to the rotor 11 and which moves along the resistive element 21 as the rotor rotates on the section 14 of the shaft 12; and the center connector 23, which contacts the contactor. Terminal 24, which is connected to the center connector, extends outside of the control to provide means for connecting the unit into an electrical circuit as also do terminals 25 and as which are connected to the ends of the arcuate resistive path 21. The portion 19 of the flange l8 and ii) the lug 29, described above, are usually arranged so that the contactor will not travel past the end of the arcuate path in each direction.

Both the base it and the rotor ll are made of nonconductive insulating material to allow the variable resistor to be adjusted without any danger of shock to the operator. To assist in the adjusting of the variable resistor, teeth 27 are provided on the periphery of the rotor.

The switch which forms part of this unit comprises the stationary contact 29 which is a spherically shaped boss on the enlarged head 13 of the shaft 12, and the movable contact E li, which is shown as an integral part of the arm 31 of the U-shaped member 32. The U-shaped member is made of resilient conductive material such as brass. it is formed with two arms which are arranged to embrace the control so that the arms engage opposite sides thereof. The arm 31, which as described above acts as the carrier of the movable Contact 3d, is arranged to resiliently hold the contact against the stationary contact 29. The other arm 33 is attached to the base of the variable resistor by an adhesive resin or other appropria'. means.

The other arm 33 is equipped with the outwardly extending members, 34 and 35, which provide a terminal for the switch and which also act as locating lugs for mounting the unit. As illustrated, these members are integral parts of the arm E3, and are formed from this arm simply by cutting and bending a portion of the metal outwardly at a 90 angle therefrom. The arm 33 is also provided with a key hole shaped opening 36, which is sufficiently large to allow the arm to be attached to the base In and yet be spaced from the end 16 of the shaft L2 which acts as the other terminal of the switch. The key hole shaped opening facilitates the assembly of the unit.

The opening and closing of the switch is accomplished by the cam 37, which is carried by the rotor 11. The cam has a curved surface 38 and a fiat surface 39 as illus trated in FIGURES and 6. To improve the switch action toprovide an inclined surface to engage the cam 37, a portion of the arm 31 is bent downward to form a V-shaped protrusion ill, which has the two inclined sides ll and as also shown in FIGURES 5 and 6. This protrusion is located in the path of the cam 37 so that the curved surface 328 of the cam will engage the inclined surface 42 and force the arm 31 upwardly, moving the movable contact 3:9 out of engagement with the stationary contact 29 thereby opening the switch. After the protrusion ll) has moved out of engagement with the curved surface of the earn, it engages the fiat surface 3), which is a suficient distance above the rotor to maintain the switch open. This surface may be of varying lengths,

depending upon the number of degrees of rotation the switch open condition is desired. For example, in the commercial embodiment of this unit, the switch is open for approximately 29 of rotation of the rotor. The curved surface 38, is approximately twice the height of the flat surface 3%, so that the operator will feel a snap action when the switch moves from a closed to open condition and vice-versa.

Another important feature or'this invention is the wi ing action which occurs between the contacts when the switch is opened and closed. This wiping action is the result of the shape arrangement of the contacts plus the fact that the movable contact is carried bya resilient member which is capable of moving laterally and longitudinally, as well as vertically. When the switch is opened and closed, the arm 31 is moved vertically upward moving the contact 30 out of engagement with the stationary contact 29. This movement, greatly enlarged of course, is illustrated in FIGURE 7. By forming the contacts with generally spherical surfaces and by offsetting the central axes of the spherical surfaces, the point of contact between the two contacts will move from the point A to the point B (the distance C) when the switch is close due to the force being exerted by the spring arm 31. In

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other words, when the contact fit} is allowed to move downward to first engage the contact 2?), it will do so at the point A. Then as the spring 31 continues to exert a downward force on the contact, the resultant horizontal component of this force will cause the arm 31 to move longitudinally allowing the contact 35 to move down the contact 29 to the point B. When the switch is opened the reverse occurs, of course, and the point of contact between the contact and contact 29 moves from the point B to the point before they break engagement.

This wiping motion as described above and as illustrated FIGURE 7 is what would take place if the arm 31 moved directly upward and was allowed to return directly downward without any extraneous forces being exerted on arm. De to the configuration of the cam and the protrusion ill, however, this is not the case. When the cam 37 first engages the inclined side of the protrusion 4%, it exerts a force which has a horizontal as well as a vertical component. This horizontal component causes the arm 31 to move laterally a small amount concomitantly with the upward movement imparted to the arm by the vertical component. This same horizontal component is also pre cut when the switch is being closed since the spring action of the arm causes the protrusion 48 to move rapidly down the curved surface as of the cam 37. As a result of this hor ontal force, the point of contact between the two contac as the swi i1 is being opened and closed does not to. ow the line AB as illustrated in FIGURE 8, but follows the dotted line from A to B and back to A". A being the point of contact when the switch is being closed and A" being the point where tae contacts break engagement when the switch is being opened. The reason why these two points are spaced apart is due to the fact that the horizontal component resulting when the switch is closing is not as great as the one which is excried on the arm when the switch is being opened, since cam is moving away from the protrusion when the switch is being closed and the normal force existing between the protrusion A l and the cam 37 is not as great at that time as it is when the switch is being opened by the cam 3'7.

This wiping action which takes place between the two contact as the switch is opened and closed is very desirable in switches as is well known by those skilled in art.

In operation, the unit operates in the conventional By rotating the rotor or knob 11, the switch is either opened or closed and the contactor 1,2 is moved along the resistive element 21.

As stated above, the most common apgilication of the commercial embodiment of this control is in hearing aid units mounted in the temple of the eyeglasses of the wearer. in this application the only knob needed to be exposed for adjustment by the oeerator is the rotor ii which greatly simplifies the mounting of the hearing aid control in the eyeglass temple. in addition, the unique arrangement of parts which allows parts of the variable resistor to function also as switch components and viceversa, results in a substantial reduction in the space required for the combination control. As an exarnple of the space savings afforded by thi invention, the commercial embodiment of this control is only 905 in diameter move along the resistive path as the member is rotated on the shaft;

a Ll-shaped resilient member having a first arm and a second arm embracing the control;

the first arm being attached to the base and the second arm being resiliently urged toward the end of the shaft adjacent the rotating member; and

cam means carried by the member for engaging the second arm and forcing the second arm away from and out of electrical contact with the shaft during a portion of the rotation of the member.

2. A switch comprising:

a stationary contact having a generally spherical surface;

a U-shaped member of resilient material having a first and second arm arranged with the first arm fixed with respect to the stationary contact, and with the second arm resiliently urged toward the stationary contact;

a generally spherically shaped contact carried by the second arm; and

means for moving the contacts into and out of engagement, said contacts being arranged with their vertical axes offset so that the contacts will make and break contact with a wiping action.

3. An electrical control comprising, in combination:

a variable resistor having a stator section and a rotor section mounted on a common shaft, resistive and conductive paths, and contact means supported by the stator and rotor sections and arranged so that as the rotor section is rotated on the shaft relative to the stator section the contact means will move along the resistive path; and

an electric switch having a stationary contact and a movable contact resiliently biased into engagement with the stationary contact; cam means carried by the rotor section of the variable resistor and arranged to hold the movable contact out of engagement with the stationary contact during a portion of the rotation of the rotor, the switch being further characterized by the fact that the stationary contact is the end of the shaft of the variable resistor.

4. The electrical control of claim 3 in which the movable contact of the switch is carried by a U-shaped electrically conductive resilient member with one leg of the member being attached to the stator section and the other leg being arranged to resiliently hold the movable contact in engagement with the end of the shaft which supports the rotor.

5. The electrical control of claim 4 in which the movable contact and the stationary contact are spherically shaped and arranged with their vertical axes offset so that the contacts will make and break contact with a wiping action.

6. The electrical control of claim 4 in which the leg of the member which holds the movable contact in engagement with the stationary contact is provided with a V-shaped protrusion arranged to engage the cam means.

7. A combination variable resistor and switch comprising, in combination:

a stator section for the variable resistor comprising a flat-sided base of insulating material, an arcuate resistance element supported by the base, and a shaft of conductive material fixed to the base and extending outwardly from both sides thereof;

a rotor section for the variable resistor comprising a disc of insulating material rotatably mounted on the shaft adjacent the resistance element, and a contact carried by the disc arranged to move along the resistance element as the disc rotates on the shaft;

a U-shaped member secured to one of the sections, a stationary contact formed on one end of the shaft, a movable contact disposed on an arm of the U- shaped member resiliently biased into engagement with the stationary contact; and

cam means carried by the rotor section of the variable resistor arranged to engage a protrusion on the arm of the U-shaped member and hold the movable contact out of engagement with the stationary contact during a portion of the rotation of the rotor section;

said switch being further characterized by the fact that the movable contact and the stationary contact are spherically shaped and arranged with their vertical axes offset so that the contacts will make and break contact with a wiping action.

References Cited in the file of this patent UNITED STATES PATENTS 2,625,629 Coldwell Jan. 13, 1953 2,877,328 Bourns Mar. 10, 1959 2,887,554 Smith et a1. May 19, 1959 FOREIGN PATENTS 749,161 Great Britain May 16, 1956 

1. A COMBINATION VARIABLE RESISTOR AND SWITCH COMPRISING: A BASE OF NON-CONDUCTIVE MATERIAL; AN ARCUATE RESISTIVE PATH SUPPORTED BY THE BASE; AN ELECTRICALLY CONDUCTIVE SHAFT ATTACHED TO AND EXTENDING PERPENDICULARLY THROUGH THE BASE; A NONCONDUCTIVE MEMBER ROTATABLY MOUNTED ON THE SHAFT ADJACENT THE RESISTIVE PATH; A CONTACTOR CARRIED BY THE MEMBER AND ARRANGED TO MOVE ALONG THE RESISTIVE PATH AS THE MEMBER IS ROTATED ON THE SHAFT; A "U-SHAPED" RESILIENT MEMBER HAVING A FIRST ARM AND A SECOND ARM EMBRACING THE CONTROL; THE FIRST ARM BEING ATTACHED TO THE BASE AND THE SECOND ARM BEING RESILIENTLY URGED TOWARD THE END OF THE SHAFT ADJACENT THE ROTATING MEMBER; AND CAM MEANS CARRIED BY THE MEMBER FOR ENGAGING THE SECOND ARM AND FORCING THE SECOND ARM AWAY FROM AND OUT OF ELECTRICAL CONTACT WITH THE SHAFT DURING A PORTION OF THE ROTATION OF THE MEMBER. 